1. Field of the Invention
The present invention relates to a pressure intensifier for fluids, particularly for hydraulic liquids. The pressure intensifier includes a piston/cylinder arrangement with a low pressure side provided with a low pressure connection and a high pressure side provided with a low pressure connection and a supply connection, as well as an intensifier piston constructed as a double diameter piston arranged between the low pressure side and the high pressure side. The pressure intensifier further includes a valve slide member which alternatingly connects the low pressure connection to a pressure source and a negative pressure source, wherein the control valve is connected through a control line to the piston/cylinder arrangement, so that the pressure in the control line acts on one side of the valve slide member.
2. Description of the Related Art
Pressure intensifiers of the above-described type have the purpose of increasing the pressure in a fluid above the pressure of a pressure source. The following explanation will be with respect to hydraulic liquids. However, the principle is basically also applicable to other fluids.
A pressure intensifier of the above-described type is known from German application 40 26 005 A1. As is the case in the present invention, the known pressure intensifier is provided with a double diameter piston which acts as an intensifier piston. The intensifier includes a low pressure piston which is arranged in a low pressure cylinder and a high pressure piston which is arranged in a high pressure cylinder. Both pistons are rigidly connected to each other through a piston rod. The low pressure piston has a substantially greater cross-section than the high pressure piston. The pressure intensification between the low pressure side and the high pressure side then takes place in accordance with the ratio of the piston cross-sections. In this case as well as in the following description, the terms "low pressure" and "high pressure" are only used for distinguishing the two sides. The terms do not reflect absolute pressure values, but only relative relationships.
Hydraulic liquid is frequently removed from the high pressure side, wherein the hydraulic liquid must be replenished with the appropriate pressure. For this purpose, the high pressure cylinder, i.e., the pressure space acted upon by the high pressure piston, is filled with hydraulic liquid which is supplied from the pressure source. This causes the high pressure piston, and with it the low pressure piston, to be pushed back. The low pressure piston then displaces the hydraulic liquid out of the pressure space to the tank. Once the high pressure piston has been pushed back by a certain distance, the high pressure piston releases the opening of the control line, so that the pressure of the pressure source can act on the slide member of the control valve. The control valve is constructed as a three-way valve. When the appropriate pressure has been applied, the connection between the low pressure cylinder and the tank is interrupted and a connection between the pressure source and the low pressure cylinder is effected instead. The low pressure piston, and with it the high pressure piston, are then pushed back in the direction toward the high pressure side, so that the hydraulic liquid can be discharged through the high pressure connection at the appropriately high pressure.
In the known arrangement, the valve slide member is acted upon on one side by the pressure of the control line and on the other side by the force of a spring.
When more hydraulic liquid is to be taken out at the high pressure connection, the frequency increases at which the intensifier piston, on the one hand, and the valve slide member, on the other hand, must be moved back and forth. An increase in size of the piston/cylinder unit is possible only to a limited extent. On the one hand, this would mean that the time required for filling the high pressure side is longer. On the other hand, the mass increases, so that a fast reciprocating movement of the intensifier piston becomes more difficult. This means that the quantity that can be discharged is limited. In an embodiment of the pressure intensifier known from German patent application 40 26 005 A1, the maximum discharged quantity on the high pressure side was about 2.5 l/min, which corresponds to a maximum supplied quantity of about 10 l/min and which required a frequency of 30 Hz.